The present invention relates to digital data communications, and more particularly, to systems and methods for accommodating terminals of different throughput capabilities.
Current systems use a variety of schemes for encoding and multiplexing digital data streams for communications between terminals including frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA). Some systems have also been devised which use various combinations of FDMA, TDMA, and CDMA.
One problem with known prior art systems, however, is that they do not readily accommodate terminals having different throughput capabilities in an integrated digital network. In particular, data communications systems using TDMA and satellite relay typically expect or require that all terminals interconnected in the network have similar throughput capabilities and use a common modulation. In addition, these conventional systems cannot accommodate terminals that transmit at significantly different burst rates, and thus require all the terminals to use antennas of approximately the same diameter.
Conventional communications systems using FDMA and satellite relay, or any other form of radio relay, can accommodate multiple isolated point-to-point channels of differing throughput in configurations normally referred to as stove-pipe architectures, where integrated digital networking is not practically feasible.
Conventional TDMA systems that use variable rate burst modems can accommodate channels of differing throughputs. These systems, however, inefficiently use equipment at sites with relatively large antenna diameters by requiring a large number of modems to handle communications with smaller terminals.
Conventional satellite, or any other form of radio relay, systems using CDMA typically cannot handle reception of signals at varying power levels from different terminals, a problem normally referred as the xe2x80x9cnear-far problem.xe2x80x9d
Therefore, there exists a need to overcome the above described problems of the prior art and thus permit a system that accommodates terminals of different throughput capabilities in an integrated digital network.
Accordingly, the present invention is directed to methods and systems for communicating between nodes that substantially obviates the problems of prior art communications systems.
In accordance with the purposes of the invention, as embodied and broadly described herein, the invention comprises a method for communicating over a network having a plurality of nodes. The method comprises the steps of generating a plurality of codes each being orthogonal to and a circular shifted version of every other one of the codes, assigning a subset of the codes to a first node, and transmitting information from the first node to a second node using the subset of codes.
In another aspect, the invention comprises a node for communicating over a network including means for storing a subset of codes, and means for transmitting information from a first node to a second node using the subset of codes. The subset of codes is derived from a set of codes and each code in the set of codes is orthogonal to and a circular shift of every other code in the set of codes.
In still another aspect, the invention comprises methods for modulating end-user information in symbols wherein each symbol is capable of carrying multiple bits of information.
In still another aspect, the invention comprises systems and methods for communicating between nodes using circulant-unitary matrices.
This summary of the invention and the following detailed description should not restrict the scope of the claimed invention. Both provide examples and explanations to enable others to practice the invention. The accompanying drawings, which form part of the description for carrying out a best mode of the invention, show several embodiments of the invention, and together with the description, explain the principles of the invention.